To strip de HTML code in a SSRS report you can use the following Function:
Public
FUNCTION RemoveHtml(ByVal Text As String) AS String
IF Text IsNot Nothing Then
Dim objRegExp AS NEW System.Text.RegularExpressions.Regex("<(.|\n)+?>")
RETURN objRegExp.Replace(Text, "")
END IF
END Function
1. Go to your report. Click Report à Report Properties

2. Paste the code (In the beginning of this article) into the Code tab.

3. Now you can use the RemoveHtml function in your textbox with an expression.

Note. The function will not be recognized by SSRS en will be underlined in red